The number of flex-fuel vehicles in circulation is increasing.
The commonest type of alcohol participating in the makeup of the fuels currently provided on the market is ethanol. It is present therein in proportions which can vary according to the countries. In some countries, in particular in Brazil, the ethanol-based fuel commonly used exhibits a theoretical ethanol content of 100% and corresponds to the denomination E100.
Such E100 fuels are not, however, devoid of traces of water, due in particular to the hydrophilic nature of this alcohol. While water contents of these fuels of less than 5% are common and without significant consequence with regard to the operation of the engine, it frequently happens, depending on the storage conditions and time of the fuel, that this water content rises above this value, sometimes even up to 12 or 15%.
It is thus possible, in flex-fuel vehicles (FFVs), to have present a mixture of alcohol, gasoline and water, in variable respective contents, as a function of the type of residual fuel present in the tank when it is refilled and of the type of fuel introduced during this refilling.
In point of fact, the presence of an excessively large amount of water in the fuel furthermore comprising alcohol has harmful consequences with regard to the operation of an engine, in particular under “cold” operation conditions, that is to say conditions under which the temperature of the liquid coolant of the engine does not exceed 30° C. Mention may be made, by way of example, of an instability in combustion during the warmup of the engine which is effected in particular by the lighting of warning lights on the dashboard, ignition problems, impossibility of keeping the engine idling, a starting time increased by 3 to 20 seconds, the stalling of the engine under transient conditions, and the like. In the worst situations, it may be impossible to start the engine.